https://arstechnica.com/gadgets/2017/09/apples-new-file-system-will-eventually-support-fusion-drive-machines/ >MacOS High Sierra just came out of beta and is available to the public, but some users may feel left out by the current limitations of Apple's new file system (APFS). The new system currently supports machines with all-flash built-in storage, so those with Fusion Drives can't use it. However, a report from MacRumors cites an e-mail to a reader from Apple's Craig Federighi that states APFS will support Fusion Drives with later software updates. Apple confirmed to Ars that this is the case: support for Fusion and HDD systems will come in future updates.